Heretofore, such as shown in U.S. Pat. No. 3,596,774, dated Aug. 3, 1971 and U.S. Pat. No. 3,731,771, dated May 8, 1973, end-of-car hydraulic-pneumatic cushioning devices for railway cars have been provided in which liquid and gas fluids have been in direct contact with each other in a mixture. However, these prior art devices have provided means to provide at least a partial separation of the gas and liquid fluids. In some instances, a separate air chamber has been connected to a hydraulic fluid chamber by ports and a tubular member has been provided through which the air or gaseous fluid must pass in order to be mixed with the liquid in the high pressure chamber of the cushioning devices. A pre-load pressure of around 200 to 600 psi is provided for the hydraulic cushioning device when employed in an end-of-car cushioning arrangement. An end-of-car cushioning device is usually designed for a speed which provides an impact force of 500 kips or 500,000 pounds. At such impact loads, pressures within the high pressure chamber of the hydraulic-pneumatic cushioning unit having an inside diameter of around 9 inches will be about 8,000 psi which is distributed over the volume of the high pressure chamber. While heretofore it had been expected that the gas escaped to the top of the chamber, this has not been paticularly true as much of the gas has been entrapped in the liquid and has formed a foam in some instances. However, in practice, the gas and liquid mixture or foam has not been found to have any material effect on the operation of the cushioning device.